Role of phosphate in microalgal-bacterial symbiosis system treating wastewater containing heavy metals

This study investigated the roles of phosphate on the response of the MABS system to Zn2+. The results showed that the pollutant removal effect in the MABS system was significantly reduced, and microbial growth and activity were inhibited with the presence of zinc ion (Zn2+). When phosphate and Zn2+ coexisted, the inhibition effects of pollutants removal and microbial growth rate were mitigated compared to that of only with the presence of Zn2+, with the increasing rates of 28.3% for total nitrogen removal, 37% for chemical oxygen demand removal, 78.3% for chlorophyll a concentration, and 13.3% for volatile suspended solids concentration. When phosphate was subsequently supplemented in the MABS system after adding Zn2+, both pollutants removal efficiency and microbial growth and activity were not recovered. Thus, the inhibition effect of Zn2+ on the MABS system was irreversible. Further analysis showed that Zn2+ preferentially combined with phosphate could form chemical precipitate, which reduced the fixation of MABS system for Zn2+ through extracellular adsorption and intracellular uptake. Under Zn2+ stress, the succession of microbial communities occurred, and Parachlorella was more tolerant to Zn2+. This study revealed the comprehensive response mechanism of the co-effects of phosphate and Zn2+ on the MABS system, and provided some insights for the MABS system treating wastewater containing heavy metals, as well as migration and transformation of heavy metals in aquatic ec...
Source: Environmental Pollution - Category: Environmental Health Authors: Source Type: research